ABSTRACT Since their introduction to the United States (US), the prevalence of electronic cigarettes (ECIGs) has risen markedly. In 2016, rates of use among high school students was estimated to be 11% and 3.2% among adults. There is considerable heterogeneity in ECIGs, but common to most is that they use an electrically-powered heater to aerosolize a liquid usually (though not always) containing nicotine, a solvent (e.g., propylene glycol and/or vegetable glycerin), and flavorants. The power (Watts=V2/?) of the ECIG device, which is based on the device?s operating voltage (V) and heater resistance (Ohms or ?), is a major determinant of how much nicotine or other toxicants are aerosolized. Recent population based surveys are providing insight into ECIG use patterns, but there are significant gaps in our understanding of ECIG behavioral and health effects. Many surveys are producing mixed results with respect to whether or not ECIGs aid in smoking cessation efforts or if there are potential harmful health effects of ECIG use. Heterogeneity in ECIG products that include low power disposable devices, higher power modular devices, and newer ?pod mods? such as JUUL, leads to difficulty in assessing device characteristics with self-report surveys and may contribute to these mixed and inconclusive findings. Recent data from our group shows that users of ECIGs are not able to report the power of their device accurately. As noted in RFA-OD-18-003, studies are needed to determine ?how product design characteristics (and changes in those characteristics) impact constituent exposures and toxicities from tobacco products.? The premise of this application rests on a growing consensus in the field that in order to inform policy, regulation, and the public health impact of ECIG use, researchers must improve methods to quantify ECIG device characteristics and how much ECIG liquid is ingested. In order to advance research in this area, we propose the development of a novel tool to assess ECIG power objectively in real-world settings. We propose adapting a method being used in the field of dietary assessment whereby pictures of food are evaluated to measure food intake and the nutritional quality of the diet. We will apply this methodology to assess ECIG device characteristics and liquids. Using an iterative design and evaluation process, we will develop a smartphone app (SmartVape) designed for an ECIG user to capture an image of their device and their liquid(s). On a back-end server, an operator will be able to compare these images to an image-based product registry with known data on device characteristics and ECIG liquid nicotine content. The result will be the ability to assess accurately the ECIG device being used and the amount of liquids being consumed over a discrete period of time. With this information, we will be able to estimate nicotine intake more accurately from ECIGs in real-world settings. Successful completion of the aims will move the field forward significantly as it would provide a feasible and objective method for assessing heterogeneity in ECIG device characteristics in surveillance research and offer an innovative method to remotely quantify ECIG liquid intake, both of which are barriers that hinder our understanding of the toxicity of ECIG use.